Filter apparatus for hydraulic system

ABSTRACT

A filter for a hydraulic system which filter is mounted within the reservoir containing the hydraulic fluid supply. The filter comprises a yieldably mounted cylinder element that is normally biased towards a closed filtering position, said filter element being adapted to yield to an open position at such times as porous side walls of the filter element become clogged to the extent that a predetermined back pressure is imposed by the filter element on the flow passing therethrough. The apparatus is further characterized by a filter condition sensing and indicating means that senses only that pressure build-up within the filter element which is caused by clogging of the porous walls of the element. Hence, false condition indications due to flow surges inherent in filtered systems are eliminated.

[ 1 Jan. 22, 1974 United States Patent [191 Raymond FILTER APPARATUS FORHYDRAULIC surement: Static Pressure, p. 5-5, 4th Edition, 1963.

Sampling Particulate Matter, R. L. Solnick, The Oil and Gas Journal,10-15-56, pages 120-124.

SYSTEM [75] Inventor:

Robert E. Raymond, Zanesville, Ohio [73] Assignee: International BasicEconomy Primary Examiner-Samih N. Zaharna Corporation, New York, NY.Assistant ExaminerRobert H. Spitzer Attorney, Agent, or FirmPalmer FultzJune 26, 1972 [22] Filed:

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Continuation of Ser- No. 03 7 D 31 1970 A filter for a hydraulic systemfilter is mounted abandoned.

within the reservoir containing the hydraulic fluid supply. The filtercomprises a yieldably mounted cylinder element that is normally biasedtowards a closed filtering position, said filter element being adaptedto yield to an open position at such times as porous side walls of thefilter element become clogged to the extent that 24.4 31 1 /0 /5 O30,G 1.1HD 0 0 an H m;2 0 4 a 1 2 2 "27 in ,1 0" a 9 nhml w W2 /l n W50 n3"1.1 "u Duo l WTm Tm I. S m U.mF 1]] 218 555 a predetermined backpressure is imposed by the filter [56] References Cit d element on theflow passing therethrough. The appa- UNITED STATES PATENTS ratus isfurther characterized by a filter condition sensing and indicating meansthat senses only that pressure build-up within the filter element whichis 210/90 caused by clogging of the porous walls of the element.

Rosaen 210/90 Hence, false condition indications due to flow Surgesinherent in filtered systems are eliminated.

3,572,508 3/1971 Rice 2,569,748 10/1951 Grave 3,543,934 12/1970Raymond... 3,468,420 9/1969 OTHER PUBLICATIONS Perrys Chemical EngineersHandbook, Flow Mea- 2 Claims, 7 Drawing Figures O 2 6 2 m 6 3 a. M w 4 4a it???$5,253.; a 6 5 a Z Q It: MW W r/IAIl/l/l/ 2m .ll....Siittztii:Fain; o llhblrmwmlkiisI\\\\\\\\-%Hm- .r Ill/ll :1 M m: a M 5 w 2 9 a 2 35 7 M 6 a m r a w .u 3 t a .0 r n I u m a a u 2 3 PATENTEDJANZZW3.786820 SHEET 3 [IF 3 RREssuRE DROP DATA ,5

RETURN LINE /0 PRESSURE 5 PRESSURE P PSL 5 'MAX. RATED PRE$$URE FIG. '6.lO/L FILTER ELEMENT PRESSURE- CLEAN 200 SSU 1?;

MAX. BY-PASS i FILTER APPARATUS FOR HYDRAULIC YSTEM CROSS REFERENCE TORELATED APPLICATION This application is a continuation in part of mycopending application Ser. No. 103,176 filed Dec. 31, 1970 nowabandoned.

BACKGROUND OF THE INVENTION Field of the Invention This inventionrelates generally to filters for hydraulic systems and more particularlyto'such a device that is mounted within the reservoir of a hydraulicsystem.

In general, the filter apparatus of the present invention comprises anassembly that is mounted within the reservoir of a hydraulic systemwhich reservoir supplies the fluid that is circulated through the pump,motor and other hydraulic components of the system. Such filterapparatus comprises generally a filter element mounting means, disposedwithin the bath of hydraulic fluid in the reservoir, and a cylindricalfilter element of conventional design known to the art and slideablymounted on said mounting means. The filter element is normally biasedtoward a closed filtering position wherein-the hydraulic fluid beingcirculated must pass through the porous side walls of the cylindricalfilter element.

The above mentioned mounting means is adapted to permit yielding of thefilter element to an open position at such time as the porous side wallsof the filter element become clogged to the extent that a predeterminedback pressure is imposed by the filter element on the flow passingtherethrough.

As a result of such yieldable characteristics of the filter element, itwill be understood that the filter element and its mounting means areadapted to provide a bypass relief valve action which permits thehydraulic system to continue to operate even after the filter is cloggedwith filters contaminates.

SUMMARY OF THE INVENTION Filter condition indicating means for the abovedescribed type of apparatus, as well as for other by-pass filterarrangements, inherently impose a problem in that flow surges inherentin systems being filtered produce false read-outs with respect to thecondition of the filter element. That is to say a flow build-up in asystem causes the condition indicator to show clogging when such has notas yet occured.

As a primary aspect of the present invention the filter apparatus isprovided with a novel filter condition sensing and indicating means thatsenses only that pressure build-up within the filter element which iscaused by clogging of the porous walls of the element. That is to say,the sensing and indicating means of the present invention is isolatedfrom flow surges which inherently occur in hydraulic systems beingfiltered whereby only the extent of clogging of the filter element isindicated.

As another aspect of the present invention, the above mentioned filterapparatus and mounting means are disposed within the reservoir bathwithout the need of a filter housing around the filter element andwithout the need for external piping exterior of the reservoir. As aresult, lower cost and space economy are realized.

As another aspect of the present invention, the filter element of thepresent apparatus is removable, replacable or cleanable, withoutdisturbing any other components of the hydraulic system and without theneed for shutting down the operation thereof.

As another aspect of the present invention, the filter apparatus isuniquely adapted for suction, by-pass or return line filtering with manyadditional circuit options all of which are accomplished within thereser- V011.

As another aspect of the present invention, the filter apparatus caneasily be provided with contamination indicator gauges of a standardtype, either at the filter or at remote locations.

As still another aspect of the present invention, the filter apparatus,being disposed within the reservoir bath without the need of a filterhousing immediately surrounding the filter element, functions as adiffuser for the fluid flow since the fluid is either picked up by ordischarged from the filter media through a relatively large porous areaprovided by the cylindrical wall of the filter element.

As another aspect of the present invention, the novel filter apparatusand mounting means are mounted within the reservoir by a novel'assemblywhich provides a flow conduit for the flow of hydraulic fluid, to orfrom the filter element, as well as a pressure gauge and mountingconduit for such gauge, with said assembly being removable as a unitfrom an opening in the top of the reservoir.

It is a primary object of the present invention to provide an improvedfilter apparatus and filter condition indicating means that eliminatesfalse filter condition read-outs from the occurrence of pressure surgesin the hydraulic system being-filtered.

It is another object of the present invention to provide a novel filterapparatus uniquely adapted to provide by-pass relief valve action forthe relief of surge flows or saturated contamination conditions.

It is another object of the present invention to provide a novel filterapparatus wherein the filter element is mounted directly within thehydraulic fluid bath of the reservoir without the need for a filterhousing or external piping.

It is another object of the present inventionto provide a novel filterapparatus which can easily be selectively arranged for by-pass or returnline filtering operation. I

It is another object of the present invention to provide a novel filterapparatus wherein the filter element is removable, cleanable andreplaceable without disturbing any other components of the hydraulicsystem and without the need. for shutting down operation thereof.

It is another object of the present invention to provide a novel filterapparatus which can be provided with contamination indicator means ofstandard pressure gauges mounted either at the filter location or remotetherefrom.

It is still another object of the present invention to provide a novelfilter apparatus which includes the above-mentioned features incombination with a novel mounting and conduit assembly which assemblycan be removed as a unit from an access hole in the top of thereservoir.

It is still another object of the present invention to provide a novelfilter apparatus wherein a plurality of filter elements can be stackedin series so as to provide additional area of filter media usingstandard cylindrical filter cartridge elements.

Further features and the advantages of the present invention will beapparent from the following description, reference being had to theaccompanying drawings wherein a preferred form of embodiment of theinvention is clearly shown.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view of ahydraulic reservoir showing the filter apparatus of the presentinvention mounted therein; I

FIG. 2 is an' end sectional view of the reservoir and filter apparatusof FIG. 1;

FIG. 3 is a side elevational view, partially in. section, of a filterapparatus constructed in accordance with the present invention;

FIG. 4 is a side elevational view of a modified filter apparatusconstruction in accordance with the present invention;

FIG. 5 is an end sectional view of the apparatus of FIG. 4, the sectionbeing taken along the lines 55 of FIG. 4;

'4 tions along tube portion 38. This adapts the assembly for use withreservoirs of various depths.

Details of the construction of filter condition indicator assembly 36are illustrated and described in detail in my United States LettersPatent No. 3,543,934 issued Dec. 1, 1970.

With continued reference to FIGS. 1 and 2, a clamp plate 60 and an airseal gasket 62 are disposed in overlying relationship with collar 54such that when a plurality of bolts 64 are tightened, clamp plate 60urges air seal gasket 62 into sealed engagement with top wall 24 of thereservoir and also in sealed engagement with axially adjustable collar54.

It is important to note that the tightening of bolts 64 also serves toapply axial force to collar 54 which in turn forces tube 38 downwardlyhence urging shoulder 44 on the lower end of housing 40 into sealedengage- I ment with an oil seal gasket 48 and the underlying shoulder 46which surrounds port 30.

FIG. 6 is a graphical illustration showing pressure drop data for theoperation of the apparatus of the present invention; and

FIG. 7 is a diagrammatic view of filter and filter condition indicatingapparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring in detail to thedrawings, FIGS. 1 and 2 illustrate a reservoir for a hydraulic machineor system which includes side walls 20, a bottom wall 22 and a top wall24 provided with an access opening 26. As seen in FIG. 1, bottom wall 22of the reservoir includes a port 30 for the flow of hydraulic fluidthrough the reservoir which port may be connected with the discharge ofa hydraulic pump, valves or other system components, not illustrated,whereby fluid from a bath 32 of hydraulic fluid passes through acylindrical filter element indicated generally at 34. V

In the preferred embodiment shown, the port50 is connected to thedischarge or pressure side of the pump.

With continued reference to FIGS. 1 and 2, the apparatus furtherincludes a filter condition indicator assembly indicated generally at 36which includes a tube portion 38 on the upper end of which is mountedpressure indicating indicia such as a gauge 39. The lower end of tubeportion 38 is connected to a housing portion 40 at a coupling 42, andthe lower end of said housing portion 40 includes an annular mountingshoulder 44 which confronts a second annular mounting shoulder 46carried by lower reservoir wall 22 and in surrounding relationship-withport 30.

A resilient seal or gasket 48 is disposed between shoulder 44 on housing40 and the confronting shoul der 46 carried by bottom reservoir wall 22.

In view of the above it will be noted that the tube portion 38 of thefilter assembly serves the dual function of providing a passage 68 fortransmitting pressure to gauge 39 and forming a structural member forurging lower shoulder 44 into sealed engagement with underlyingresilient oil seal 48.

In operation, when it is desired to remove the filter conditionindicator assembly 36, for example when filter element 34 becomespartially clogged as indicated by gauge 39, then the bolts 64 areremoved and the filter assembly 36 together with clamp plate 60 andgasket 62, is lifted upwardly and outwardly through access opening 26,it being understood that the tubular portion 38, must be tilted from thevertical so as to permit removal of the L-shaped assembly, including thefilter mounting means 10, whereby the filter or any portion of theassemnly can be serviced.

Referring next to FIGS. 3 5, a filter element mounting means isindicated generally at 10 and includes a first end wall 11 mounted onconduit 50, assembly 36, and a second end wall, with said end wallsbeing connected together by three guide rods 33. As seen in FIG. 3, theright end of the guide rod is mounted in threaded holes 51 in right endwall 11 and the left end of guide With continued reference to FIGS. 1and 2, housing rods 33 are threaded at 53 and provided with nuts 35whereby the left end 31 can readily be removed providing access to afilter element 34 for the removal, cleaning and replacement thereof.

With continued reference to FIGS. 3 5, a filter element 34 is in theform of a conventional cylindrical filter element, well known to theart, which includes inner and outer cylindrical side walls 18 and 19formed of perforated paper, metal or the like, and a filter media 39 isdisposed between such side walls 18 and 19 and may be in the corrugatedconfiguration shown in FIG. 5.

Filter element 34 further includes an annular shoulder 15 that surroundsa filter inlet orifice 74 with said annular shoulder being provided withan annular resilient seal portion 14 which normally engages a secondseal portion formed by the peripheral surface of end wall 11 thatsurrounds a mounting means port 13 communicating with the passage 16within conduit 50, it being understood that passage 16 communicates withport 30, FIGS. 1 and 2, via the interior of housing 40 of apparatus 36.

Referring again to filter element 34, the left end thereof includes anannular shoulder 23 which engages a resilient seal of L-shapedcross-sectional configuration which is in turn mounted on a protrusionon an end closure element 27.

As seen in FIG. 3, a resilient element or compression spring 29 isdisposed between end closure 27 and a spring mount 45, the latterincluding a threaded element 41 mounted in a bore 43 in second end wall31 such that rotation of threaded portion 41 adjusts the preload onspring 29. This permits adjustment of the predetermined pressure atwhich filter element 34 will yield to the left, as viewed in FIG. 3, andmove from the closed position of FIG. 3 to the open or by-pass reliefposition of FIG. 4.

FIG. 4 illustrates a modified embodiment which is identical to theembodiment of FIG. 3 except that the variable bias adjusting means 41 45is eliminated such that the embodiment of FIG. 4 will always effectbypass relief at .the same selected pressure setting for spring 29.

In operation, when the port is connected to the discharge side of apump, not illustrated, the flow of hydraulic fluid enters port 30,passes through housing 40, conduit 50 and then into the cylindricalhollow portion 21 of filter element 34. The fluid is thereafter filteredand diffused as it passes outwardly through the outer and inner walls 18and 19 and the filter media 39. As the system continues to operate andcontaminates are collected in the filter media 39, the resistance toflow will as a result increase and when a predetermined back pressureexerted by the filter media is reached at which pressure the forceexerted by the filter media is reached at which pressure the forceexerted by spring 29 is exceeded, then filter element 34 will shift tothe left from the closed position of FIG. 3 to the open position of FIG.4 whereby fluid from conduit 50 will be released directly from themounting means port 13 to the bath 32 of the reservoir.

It will be understood that the system will continue to operate althoughthe flow will no longer be filtered.

It should be mentioned that since the opening or bypass relief occurs atthe right end of filter element 34, the release of fluid directly to thereservoir will be upstream of the collected contaminates within thefilter media 39, such that such contaminates will be retained in thefilter media rather than being released to the reservoir bath.

With reference to FIG. 3, it should be mentioned that the net internalarea at the right end with is exposed to the pressure within the hollowportion 21 of the filter is greater than the corresponding internal areaat the left end whereby the separating force will always be such as tocause filter element 34 to shift to the left, as seen in FIG. 4, therebyreleasing the unfiltered flow directly to the bath upstream of thefilter element 34.

Reference is next made to the filter condition indicating apparatus ofthe present invention which comprises a pressure detector tube 70 whichconnects the cavity 21 in filter element 34 with tube passage 68 leadingto a filter condition indicator such as pressure gauge 39 shown in FIGS.1 and 2.

Detector tube 70 cooperates with a filter inlet orifice 74 to isolategauge 39 from reading pressure rises which occur in the hydraulic systemthereby eliminating false read-outs at gauge 39. More particularly, uponoccurrence of a flow surge in return line 30, FIGS. 1 and 2, filterinlet orifice 74 will reject surge imposed pressure rises from occurringin filter cavity 21. Hence a detector tube inner port 72 can only detectpressure rises within filter cavity 21 which are the result of cloggingof porous side wall 29 by filtered contaminants.

Operation of the above described filter condition indicating apparatusis illustrated diagrammatically in FIG. 7 and graphically in FIG. 6 fromwhich it will be seen that if the return line pressure P, rises to apreselected maximum by-pass pressure P the filter cartridge 34 shifts tothe left, from the position of FIG. 3 to the position of FIG. 4 wherebyby-pass flow O is released directly to reservoir bath 32. At the sametime, due to the location of detector tube inner port 72, and the flowrejection characteristic of inlet orifice 74 the pressure in detectortube and tube passage 68 is only that pressure within filter cavity 21which is a function of the degree of clogging of the filter element.

The graph of FIG. 6 shows a typical example of a 10 micron filterelement using 200 SSU fluid viscosity, which is acceptably clean to aninternal filter pressure Pf of 5 psi with a maximum rated filterflow of6gallons per minute and a maximum rated system flow Q, at by-pass ofgallori s per minute. i

While the form of embodiment herein shown and described, constitutespreferred form, it is to be understood that other forms may be adoptedfalling within the scope of the claims that follow:

What is claimed is:

l. A reservoir and filter apparatus comprising, in combination,reservoir means for containing a bath of fluid to be filtered andincluding a reservoir wall provided with a filter access port; a filterand filter condition indicating apparatus mounted on said reservoir walland extended through said filter access port and into said bath, saidapparatus being removable from said reservoir means as an assembly andcomprising (a) a hollow filter element comprising a porous filter walland a filter cavity provided with a filter inlet orifice; (b) by-passmeans for by-passing hydraulic fluid past said filter inlet orifice uponclogging of said porous wall; (0) a pressure detector tube including aninner detector tube port disposed in said filter cavity and an outerdetector tube port; (d) and a filter condition indicator connected tosaid outer detector tube port.

2. The reservoir and filter apparatus of claim 1 wherein said reservoirmeans includes a second reservoir wall provided with a reservoir portfor the flow of fluid through the reservoir means and a first mountingshoulder for said filter and filter condition indicating apparatus; andwherein said filter and filter condition indicating apparatus includes ahousing portion provided with a housing port communicating with saidreservoir port and a second mounting shoulder removably connected tosaid first mentioned mounting shoulder.

1. A reservoir and filter apparatus comprising, in combination,reservoir means for containing a bath of fluid to be filtered andincluding a reservoir wall provided with a filter access port; a filterand filter condition indicating apparatus mounted on said reservoir walland extended through said filter access port and into said Bath, saidapparatus being removable from said reservoir means as an assembly andcomprising (a) a hollow filter element comprising a porous filter walland a filter cavity provided with a filter inlet orifice; (b) by-passmeans for bypassing hydraulic fluid past said filter inlet orifice uponclogging of said porous wall; (c) a pressure detector tube including aninner detector tube port disposed in said filter cavity and an outerdetector tube port; (d) and a filter condition indicator connected tosaid outer detector tube port.
 2. The reservoir and filter apparatus ofclaim 1 wherein said reservoir means includes a second reservoir wallprovided with a reservoir port for the flow of fluid through thereservoir means and a first mounting shoulder for said filter and filtercondition indicating apparatus; and wherein said filter and filtercondition indicating apparatus includes a housing portion provided witha housing port communicating with said reservoir port and a secondmounting shoulder removably connected to said first mentioned mountingshoulder.